1. Field
One embodiment of the invention relates to a storage device, a processor of a storage device, and a computer program product capable of optimizing a parameter set when data is written to or read from a magnetic disk medium, and more particularly, to a storage device, a processor of a storage device, and a computer program product capable of optimizing a parameter while writing data to a magnetic disk medium and subsequently reading data from the magnetic disk medium.
2. Description of the Related Art
In conventional magnetic disk devices, when data is written to a magnetic disk, a hard disk controller converts write data received from a host device into a predetermined data format, and performs error-correcting code (ECC) encoding process to add an ECC code to the write data. Then, a write modulation system of a read channel performs scramble process, run-length limited (RLL) code conversion process, and write compensation process. Then, a write amplifier amplifies the data, and a write element of the head selected by a head integrated circuit (IC) writes the data to the magnetic disk.
When data is read from the magnetic disk, a read element of the head selected by a head selection signal from the head IC reads a signal, and a pre-amplifier amplifies the read signal. Then, the amplified signal is input to a read demodulation system of a read channel, and the read demodulation system demodulates the read data using, for example, partial response maximum likelihood (PRML) detection. Then, the demodulated data is subjected to RLL decoding process and descramble process. Thereafter, the hard disk controller performs ECC demodulation process on the data to correct an error, and the read data is transmitted to the host device.
A write system parameter and read system parameter corresponding to the characteristics of the head or the magnetic disk are necessitated for the write/read operation. Therefore, in test process after the magnetic disk device is manufactured, the write system parameter and the read system parameter are adjusted to optimal values that correspond to the characteristics of the head and the magnetic disk.
Process of adjusting the write system parameter and the read system parameter is performed for each of heads and each of zones that are divided in the radius direction of the magnetic disk. That is, a head and a zone of the magnetic disk to be adjusted are selected, and the parameters are adjusted while writing data to and reading data from a sector, which is an adjustment position, of a predetermined track in the selected zone such that the best signal quality (margin) is obtained (for example, see Japanese Patent Application (KOKAI) No. H5-142317 and Japanese Patent Application (KOKAI) No. H10-91908).
However, in the conventional parameter adjustment process, the adjustment position is fixed to a position of a sector of a predetermined track in a selected zone of a magnetic disk corresponding to a selected head, and thereafter, the data is written to the adjustment position, and the data is subsequently read from the sector, to optimize the parameters. Therefore, it is sometime difficult to optimize the parameters of certain magnetic disks. Accordingly, in the worst case, when the write/read operation is performed after the parameters are adjusted, defect error in medium that cannot be recovered occurs. In addition, the write and read performances deteriorate due to alternating process.
Even when the parameters are optimized, the error occurs due to the quality of the magnetic disk in the manufacturing process. In general, there exists non-uniformity in the magnetic disk in the manufacturing process, so that there is an attempt to uniformize the medium. However, there is a limitation in uniformizing the medium. In addition, when the recording density of the magnetic disk increases, the non-uniformity becomes apparent in the magnetic disk.
The non-uniformity of the magnetic disk occurred through the manufacturing process causes the unevenness of the in-plane coercivity in the magnetic disk medium.
Conventionally, when there is the variation in the in-plane coercivity in the magnetic disk, the data writing, the data reading, and the adjustment of the parameters such that the best signal quality is obtained, are performed at a particular position. In other words, conventionally, the parameters are not adjusted by taking into account the variation in coercivity.
Therefore, when there is a large variation in the in-plane coercivity in the magnetic disk and the parameters are adjusted using a sector with low in-plane coercivity as an adjustment position, the write performance becomes insufficient at a position where the in-plane coercivity is high. Accordingly, in the worst case, an unrecovered error occurs due to the medium defect.